Optical activity and enantioemric excess

• Applicant: Privatdozent Dr. Aras Kartouzian
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573621553

This research proposal aims to deepen the understanding of the relationship between optical activity and enantiomeric excess (ee) in chiral films, focusing on the anisotropy factor (g), which quantifies differential responses to left and right circularly polarized light. While linear g-ee dependence is common in non-interacting systems (e.g., dilute solutions), nonlinear dependencies—particularly positive (Majority-Rules Effect, MRE) and negative (Racemate-Rules Effect, RRE)—are observed in interacting systems. These nonlinear effects, linked to chiral amplification and structural preferences, are critical for applications in asymmetric catalysis, pharmaceuticals, and chiroptical sensing. However, most studies focus only on pure enantiomers or racemic mixtures, neglecting intermediate ee values. The proposal seeks to systematically investigate g-ee dependence in chiral films, combining linear (CD, CPL) and nonlinear (SHG-CD, SHG-ORD) spectroscopic techniques to correlate optical activity with structural features. The project is structured into four objectives: (1) surveying g-ee dependence in diverse chiral films, (2) understanding structural origins of nonlinearity, (3) testing stability under external conditions (temperature, humidity, light), and (4) exploring applications in chiroptical sensing and spintronics. By elucidating the mechanisms behind these effects, the research aims to enable the rational design of chiral materials with enhanced optical and functional properties. The findings could advance applications in biosensing, asymmetric synthesis, and chiral optoelectronics, where precise control over enantiomeric composition is crucial.

• DFG Programme: Research Grants